The invention is based on an electronically commutated electrical machine, in particular a motor, as generically defined by the preamble to claim 1.
In a known electronically commutated motor, also known as a brushless motor, of this type (German Patent Disclosure DE 197 25 525 A1), the coils of each winding phase of the two-phase stator winding are wound with their coils around every other tooth, with the direction of winding changing upon each successive coil. A total of eight teeth are wound. In multi-phase windings where k greater than 2, the number n of teeth n=kxc2x7v, where v is an even-numbered multiple. In a four-phase winding, that is, a stator winding with four phases, at a multiple v=2 once again eight teeth are produced.
The winding diagram of the stator winding in the known motor is shown in FIG. 1 in a four-phase version (k=4) with four parallel branches (l=4) and two series-connected coils per branch (m=2). In the four winding phases 21, 22, 23, 24, which each include all the coils 20 of one winding phase, two strands 21, 22 on the one hand and 23, 24 on the other are wound onto the same teeth via the same slots. The contact hooks for the strand terminals are identified by the symbols B1, B2, A2, A1, and the contact points for the star points, of which two star points each, belonging to the respective winding phases 21 and 22 on the one hand and 23 and 24 on the other, are combined, are marked SB and SA. All the contact hooks are disposed on the inner edge of the annular stator, on the same side of the stator. The wire segments of the winding wire, leading from the contact hooks to the coils and from one coil to the next, in the winding are also laid along the lower edge of the stator, on the same face end, in the circumferential direction. In FIG. 1, the rectangles represent the individual coils 20 wound onto the teeth. The numerals 1-16 next to the rectangles are the ordinal numbers of successive slots in the circumferential direction between the teeth, on the one hand, and the auxiliary teeth, on the other. The caption xe2x80x9cHooksxe2x80x9d designates the contact hooks both for the phase terminals B1, B1, A2 and A1, and for the star points SB and SA, which electrically and mechanically connect the respective four parallel branches of the winding phases 21-24 with a respective two series-connected coils 20. The arrowheads shown in the winding wire segments between coils 20 indicate the direction in which the winding wire runs. The winding of the teeth can be seen from the slot sequence; the tooth located between slots 1 and 2 is wrapped multiple times from slot 1 to slot 2, which is expressed by the caption xe2x80x9cslot/slot 1-2xe2x80x9d.
The winding wire course illustrated in the winding diagram of FIG. 1 for producing the stator winding is not optimal in terms of the fact that the winding wire when suspended from the hooks of the associated star point SA or SB must often be laid over long distances on the face end of the stator, resulting in a high number of conductors in that region.
The electronically commutated or brushless electrical machine, in particular motor, of the invention as defined by the characteristics of claim 1 has the advantage of a stator winding structure that is both simple and optimized in terms of production. By the contacting according to the invention of individual branches of each winding phase at the star point of another winding phase, the wire segments leading from one coil to another can be much better distributed around the stator, and the number of encompassing wires can be minimized. The wire segments that connect the coils can be optimized in terms of their length, so that because the resistances are approximately the same, an improvement in the symmetry of the phases can be achieved, and thus in the case of the motor, a better supply of electrical current is made possible.
By the provisions recited in the other claims, advantageous refinements of and improvements to the electrical machine, in particular the motor, recited in claim 1 are possible.
In a preferred embodiment of the invention, the stator winding is embodied as four-phase (k=4), with four parallel branches per winding phase (l=4); respective winding phases of the stator winding whose coils are wound onto the same teeth are contacted at a common star point. Two branches per phase are carried to the common star point belonging to that phase, and another two branches per phase are carried to the other star point and contacted at that other star point. The star points are electrically connected to one another at an arbitrary point.